The present invention relates to a door lifter for coke ovens.
Conventional door lifters of the type, which are mounted on a coke pusher and a coke guide trolley, have made door removal in such a manner that a hydraulic cylinder is so operated that upper and lower hooks of the lifter are lifted to be placed into engagement with corresponding upper and lower lug pieces of the door. Thereafter latching bars of the door are released and the hydraulic cylinder is further so operated that the door is lifted by a predetermined height from the hooking level. Next, after the door is removed away from the door frame provided at the inlet of the coke oven, the door is further lifted with the hydraulic cylinder and maintained at a predetermined final height for cleaning or other purposes. In order to reengage the door with the door frame, the sequence for door removal must be exactly reversed.
To this end, the hydraulic control system or circuit for controlling the hydraulic cylinder must include memory means which can memorize not only a first height at which the hooks are engaged with the lug pieces but also a second height at which the door is removed away from the door frame. A typical example of such hydraulic control systems has been featured by the provision of three sets of solenoid operated valve circuits and two sub-cylinders for memorizing said first and second heights, respectively. As a result, the hydraulic control system is very complex in construction and is very expensive so that the door lifters themselves become expensive.
The present invention was made to overcome the above and other problems encountered in the prior art door lifters for coke ovens and has for its object to provide a door lifter for coke ovens which has a hydraulic control system which is very simple in construction and very easy in maintenance.
Another object of the present invention is to provide a door lifter which, even when the door is not in parallel with the door lifter, can correctly engage the hooks with the lug pieces of the door.
A further object of the present invention is to provide a door lifter of the type described above which can be manufactured at less costs.
The above and other objects, effects and features of the present invention will become more apparent from the following description of preferred embodiments thereof taken in conjunction with the accompanying drawings.